Infestation Level of Helicoverpa Armigera (Hubner) in Different Tomato Varieties in Selected Districts of Khyber Pakhtunkhwa, Pakistan

Abstract

The study compared the dynamics of infestation of Helicoverpa armigera (Hubner), associated fruit damage, and yield losses in six tomato varieties (Red King, Rio Grande, Florida King, Roma, Sahel, and 1359) in 2020 and 2021, and their correlation with weather parameters in three districts of Khyber Pakhtunkhwa, Pakistan (Peshawar, Bajaur, and Swat). The level of infestation was considerably different during the growing season, with the first appearance of eggs in the 11th meteorological week, followed by the appearance of larvae in the 13th week, peak population in the 19th week, and gradual decline in the 21st week in all locations and varieties. The lowest infestations were recorded in Sahel (1.24-1.87 eggs plant^-1 and 1.241.56 larvae plant^-1) and Rio Grande (1.942.58 eggs plant^-1 and 1.72 2.58 larvae plant^-1). Temperature significantly affected the level of infestation, with the highest population being at 20–26 °C and 27–30 °C. Relative humidity had significant negative relationships with the population of larvae in all districts and years, as compared to rainfall, which had no significant effect because it had low occurrence during the cropping season. Infestation varietal variations were directly converted into fruit damage and loss of production. Damage to fruits fell between 19.97 with Roma and Rio Grande experiencing the greatest damage, and Sahel and 1359 had the lowest damage in all the districts. There is a negative correlation between the infestation intensity and yield performance, where Sahel and 1359 gave the best yield (a maximum of around 15,800 kg ha^-1), and Rio Grande and Florida King were the lowest yielders. Correlation analysis indicated that there were location-specific temperature and infestation correlations, with a significant positive correlation in Bajaur, a non-significant positive correlation in Peshawar, and a significant negative correlation in Swat. Comprehensively, the research proves that abiotic factors, especially temperature and relative humidity, and varietal resistance are major factors in determining the level of H. armigera infestation, fruit damage, and yield results. It is highlighted that it is essential to implement location-specific controls of pests and develop tolerant varieties like Sahel and 1359 to reduce losses caused by pests and increase the tomato yields.